Preheat the oven to 350°F (175°C).
Wash the zucchini, trim the ends, and grate it using the large holes of a box grater until you have about 2 cups.
In a large mixing bowl, whisk together the eggs, granulated sugar, brown sugar, applesauce, oil, and vanilla until smooth.
Stir the grated zucchini into the wet mixture.
In another bowl, whisk together the flour, baking powder, baking soda, salt, and cinnamon.
Add the dry ingredients to the wet ingredients and gently mix until just combined. Avoid overmixing to keep your Zucchini Bread Recipe tender.
Fold in the chopped walnuts if using.
Grease an 8.5 x 4.5-inch loaf pan and pour the batter evenly into the pan.
Bake for about 60 minutes, or until the loaf is golden brown and a toothpick inserted into the center comes out clean or with a few moist crumbs.
Cool in the pan for 10–15 minutes before transferring to a wire rack to cool completely.